The present invention relates to computer systems, in particular to computer systems suitable for multiprocessor systems, for example multiprocessor server systems.
One application for the present invention relates to high density computer systems, for example, computer server systems for telecommunications applications. In telecommunications applications, it is important to provide high reliability and high capacity of operation. Various approaches have been taken to providing such high-performance, high reliability systems. Typically such systems are designed around providing redundant resources so that if one component of the system develops a fault, the system remains operational using the redundant resources. Fault tolerance can also be achieved, for example, with multiprocessor systems that provide redundancy through dynamic, e.g., software-controlled, task distribution. High density systems are typically rack mountable, with one or more processor systems occupying a shelf in the rack. The trend in recent times is to make the computers with smaller form factors. This means that more computers can be located in a rack. This has the advantage of increasing the processing density within the racks, and also the advantage of reducing the distance between the computer systems.
One cause of component failure in computer systems is overheating of components. Overheating of components may cause intermittent temporary or permanent failures. Such failures are incompatible with a requirement for a computer to have a minimum downtime. Therefore, fans are regularly used to provide cooling within a computer system by drawing or pushing cool (usually ambient) air through the computer system to move air heated by virtue of being adjacent components to be replaced with cool air to provide a better temperature gradient for transfer of heat from the components to the air. Cooling fans are thus of vital importance to the operational reliability of a computer system. Therefore failure of cooling fans is a major factor in computer system reliability.
An aspect of the present invention provides a cooling fan drive circuit for driving first and second cooling fans. The circuit can include a first power conduit for providing power to each of the fans from a first power source. The circuit can further include a second power conduit for providing power to the first fan and a third power conduit for providing power to the second fan. The second and third power conduits can be arranged, in use, to provide separate connections between the respective fans and a power source other than the first power source.
An embodiment of the invention can provide a driving circuit ensuring a common mode failure for either of the first and second fans. Failure of one of the backup (second and third) power conduits does not cause a failure of the other backup power conduit, thus providing greater cooling reliability.
The first power conduit can comprise a pair of power conduits each for providing a separate connection to the first power source, whereby further power supply redundancy can be provided. The second and third power conduits can provide connections between the respective fans and a single power source. A common mode power failure for either fan can be avoided. The second and third power conduits can be connected to provide connections between the respective fans and separate power sources, whereby further redundancy can be provided in that each fan receives backup power from different power sources.
The first power supply can be located within a device enclosure within which the fans are also located, whereby reliability without wastefulness of space or wiring can be provided for cooling fans to be powered from a power source within a common housing and to receive backup power from beyond that housing.
At least one of the fans can be provided with a speed controller. This can enable increased fan life and efficient cooling based using controlled fan speeds without wasteful power usage.
The speed controller can be operable to adjust the speed of the fan in dependence upon a measured environmental variable, whereby efficient cooling fan operation can be provided by allowing the fan to be controlled to work faster when an environmental variable, such as temperature, is measured to be unfavourable, but to be able to be controlled to work slower if no unfavourable measurement of an environmental variable is made. This can enable increased fan life and efficient cooling based using controlled fan speeds without wasteful power usage.
Any of the power conduits may be provided with a softstart circuit to allow hot insertion of a computer system module including the fans into a modular computer system. This arrangement provides that a computer system module utilising the drive circuit may be made hot-pluggable, thus allowing computer system modules to be replaced without requiring the entire computer system to be powered down. Thus computer system downtime is reduced and reliability increased.
A further aspect of the present invention can provides a computer system module for a modular computer system comprising first and second cooling fans. The cooling fans can be arranged to be driven by a first power conduit for providing a power connection to each of the fans from a first power source; a second power conduit for providing a power connection to the first fan; and a third power conduit for providing a power connection to the second fan. The second and third power conduits can be arranged, in use, to provide separate connections between the respective fans and a power source other than the first power source. In such a driving circuit, failure of one of the backup (second and third) power conduits need not cause a failure of the other backup power conduit, thus providing greater cooling reliability.
Another aspect of the present invention can provide a modular computer system comprising a computer system module as set out above. Thus a computer system having high cooling reliability can be provided.
A further aspect of the present invention can provides a method of driving first and second cooling fans in a computer system. The method can include steps of providing power to each of the fans via a first power conduit from a first power supply; providing power to the first fan via a second power conduit; and providing power to the second fan via a third power conduit. The steps of providing power via the second and third power conduits can include providing separate connections between the respective fans and a power source other than the first power source. Failure of one of the backup (second and third) power conduits need not, therefore, cause a failure of the other backup power conduit, thus providing greater cooling reliability.
Further aspects and advantages of the invention will become apparent from the following description of particular embodiments.